Copy-pasted from flutter/flutter#130759:

> Today (Jul 17, 2023), I renamed the `good first contribution` label to
`good first issue`. This is because
> 1) `good first issue` is the more commonly used for this intent and
may be (ever so slightly) more recognizable to potential new
contributors, and, more importantly,
> 2) GitHub recognizes the label `good first issue` when surfacing good
first issues in specific places in GitHub[^1].
> 
> This PR updates Contributing.md to match the new name.
> 
> `grep` did not find any other references to `good first contribution`
to update in this repo.

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [ ] I listed at least one issue that this PR fixes in the description
above. _(not applicable in my opinion. If you'd like me to file an issue
first, let me know what label would be appropriate.)_
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt]. _not applicable: docs-only change_
- [x] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#overview
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[test-exempt]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#handling-breaking-changes
[Discord]: https://github.com/flutter/flutter/wiki/Chat

[^1]: [Source (GitHub
docs)](https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/encouraging-helpful-contributions-to-your-project-with-labels).
Example: https://github.com/flutter/flutter/contribute. If my vague
memory serves me correctly, this can also appear in certain emails or
the "discovery queue"-type experience that GitHub provides.

Roll Flutter from 6f09064 to d07e8ae (60 revisions)

flutter/flutter@6f09064...d07e8ae

2023-07-19 [email protected] Roll Flutter Engine from 09389b16d684 to eb2285205f25 (3 revisions) (flutter/flutter#130879)
2023-07-19 [email protected] Roll Flutter Engine from 0293a7cb7887 to 09389b16d684 (5 revisions) (flutter/flutter#130867)
2023-07-19 [email protected] Move TapAndDragGestureRecognizer code under gestures (flutter/flutter#119508)
2023-07-19 [email protected] Roll Flutter Engine from 29de67c7d009 to 0293a7cb7887 (1 revision) (flutter/flutter#130858)
2023-07-19 [email protected] Roll Flutter Engine from 39d60be72ffb to 29de67c7d009 (4 revisions) (flutter/flutter#130855)
2023-07-19 [email protected] Roll Flutter Engine from b3bfc744bb61 to 39d60be72ffb (1 revision) (flutter/flutter#130847)
2023-07-19 [email protected] Roll Flutter Engine from adf6142f6738 to b3bfc744bb61 (7 revisions) (flutter/flutter#130843)
2023-07-18 [email protected] Update app_builder_test.dart for M3 (flutter/flutter#130794)
2023-07-18 [email protected] Catch errors in loadStructuredData (flutter/flutter#130748)
2023-07-18 [email protected] Fix super tiny space formatting (hope we have auto formatter in the future) (flutter/flutter#127479)
2023-07-18 [email protected] Roll Flutter Engine from 71bbecee3010 to adf6142f6738 (2 revisions) (flutter/flutter#130831)
2023-07-18 [email protected] Update SnackBar tests for M2/M3 (flutter/flutter#130717)
2023-07-18 [email protected] Roll pub packages (flutter/flutter#130821)
2023-07-18 [email protected] Relax syntax for gen-l10n (flutter/flutter#130736)
2023-07-18 [email protected] Roll Flutter Engine from 45851af55bd6 to 71bbecee3010 (7 revisions) (flutter/flutter#130820)
2023-07-18 [email protected] Roll pub packages (flutter/flutter#130608)
2023-07-18 [email protected] Roll Flutter Engine from 831da7e9dc3b to 45851af55bd6 (2 revisions) (flutter/flutter#130814)
2023-07-18 [email protected] [Android] Deletes deprecated splash screen meta-data element (flutter/flutter#130744)
2023-07-18 [email protected] Updated `ThemeData.useMaterial3` API doc, default is `true` (flutter/flutter#130764)
2023-07-18 [email protected] [labeler] Mark sync-labels as empty (flutter/flutter#130642)
2023-07-18 [email protected] Roll Flutter Engine from c27658cc5ade to 831da7e9dc3b (2 revisions) (flutter/flutter#130810)
2023-07-18 [email protected] Roll Packages from 6889cca to 3e8b813 (9 revisions) (flutter/flutter#130802)
2023-07-18 [email protected] Update `AppBar` and `AppBarTheme` tests for M2/M3 (flutter/flutter#130790)
2023-07-18 [email protected] Update app tests for M3 (flutter/flutter#130792)
2023-07-18 [email protected] Add lint check to make sure samples are linked and have tests (flutter/flutter#130523)
2023-07-18 [email protected] Roll Flutter Engine from aaec42812a1f to c27658cc5ade (2 revisions) (flutter/flutter#130799)
2023-07-18 [email protected] Extract common functionality of iOS platformviews into superclasses (flutter/flutter#128716)
2023-07-18 [email protected] Roll Flutter Engine from 88be39be7b07 to aaec42812a1f (1 revision) (flutter/flutter#130787)
2023-07-18 [email protected] Roll Flutter Engine from b46a8baf8ed9 to 88be39be7b07 (1 revision) (flutter/flutter#130784)
2023-07-18 [email protected] Roll Flutter Engine from 777fe158f4e7 to b46a8baf8ed9 (1 revision) (flutter/flutter#130782)
2023-07-18 [email protected] Fix `iconTheme` in `AppBar` doesn't apply custom `Colors.white` in the dark mode for M3 (flutter/flutter#130574)
2023-07-18 [email protected] Roll Flutter Engine from c6e23288db8d to 777fe158f4e7 (2 revisions) (flutter/flutter#130779)
2023-07-18 [email protected] Roll Flutter Engine from 116eedf769be to c6e23288db8d (3 revisions) (flutter/flutter#130778)
2023-07-18 [email protected] Roll Flutter Engine from 9d018f00d687 to 116eedf769be (2 revisions) (flutter/flutter#130774)
2023-07-18 [email protected] Roll Flutter Engine from 77ec92371846 to 9d018f00d687 (1 revision) (flutter/flutter#130772)
2023-07-18 [email protected] Document stack's clipping behaviour better (flutter/flutter#130749)
2023-07-18 [email protected] Roll Flutter Engine from f2958f9229a4 to 77ec92371846 (1 revision) (flutter/flutter#130769)
2023-07-18 [email protected] Roll Flutter Engine from 3cceb705007e to f2958f9229a4 (1 revision) (flutter/flutter#130767)
2023-07-18 [email protected] Roll Flutter Engine from 09689d37e1d6 to 3cceb705007e (2 revisions) (flutter/flutter#130763)
2023-07-18 [email protected] Stabilize hybrid_android_views_integration_test rendering tree (flutter/flutter#130751)
2023-07-17 [email protected] update link to good first issues (flutter/flutter#130759)
2023-07-17 [email protected] Prevent `InputDecorator` from supplying its descendants with non-normalized constraints (flutter/flutter#130460)
2023-07-17 [email protected] Roll Flutter Engine from 15c15fd75743 to 09689d37e1d6 (3 revisions) (flutter/flutter#130758)
2023-07-17 [email protected] [tools/ios_build_ipa] fallback to CFBundleName if CFBundleDisplayName is absent (flutter/flutter#130752)
2023-07-17 [email protected] Resolve TODOs in channels integration test (flutter/flutter#130745)
2023-07-17 [email protected] Roll Flutter Engine from ddbe23b374d8 to 15c15fd75743 (2 revisions) (flutter/flutter#130746)
...

Today (Jul 17, 2023), I renamed the `good first contribution` label to `good first issue`. This is because
1) `good first issue` is more commonly used for this intent across GitHub and and thus may be (ever so slightly) more recognizable to potential new contributors, and, more importantly,
2) GitHub recognizes the label `good first issue` when surfacing good first issues in specific places in GitHub[^1].

This PR updates Contributing.md to match the new name.

`grep` did not find any other references to `good first contribution` to update in this repo.

[^1]: [Source (GitHub docs)](https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/encouraging-helpful-contributions-to-your-project-with-labels). Example: https://github.com/flutter/flutter/contribute. If my vague memory serves me correctly, this can also appear in certain emails or the "discovery queue"-type experience that GitHub provides.